De-extinction of species

A traditional cornerstone principle of conservation has been that when species become extinct, they are gone forever. New organisms might take over the ecological niche once occupied by an extinct species, but the process by which the original one evolved was unique and unrepeatable. Although science-fiction stories played with the idea of artificially resurrecting dinosaurs and other extinct creatures, the real scientific hurdles seemed too fantastic. Recent technological advances in sequencing and editing genomes, cloning, and manipulating stem cells, however, have encouraged some scientists to investigate whether it might not be possible to restore extinct species after all, in a process called de-extinction. See also: Biotechnology; Cloning; Cloning research; CRISPR/Cas9 gene editing; Extinction (biology); Extinction of species; Gene; Genetic code; Genetic engineering; Genetic mapping; Genomics

In theory, the de-extinction process would begin with the collection and full DNA sequencing of the genome of an extinct organism. If a species went extinct relatively recently, samples of its DNA might be extracted from well-preserved museum specimens, bits of tissues in repositories, or other archives. For species that went extinct at a more-distant time in the past, partial genomes can sometimes be collected from specimens in frozen strata and from unmineralized fossils, but this DNA is usually highly fragmented and incomplete. Nevertheless, in some such cases, scientists might be able to infer and roughly reconstruct the missing sequences from corresponding regions in the genomes of closely related living species. Once a working full genome for the extinct species was in hand, scientists could insert it into compatible egg cells (or the stem-cell equivalents) from a living species. In principle, if properly nurtured, the resulting cells would then reenact the development and gestation of the lost species. See also: Ancient DNA; Deoxyribonucleic acid (DNA); Fossil; Zooarcheology

Efforts to at least study the feasibility of de-extinction are in progress for various species, including the thylacine (also known as the Tasmanian tiger or the Tasmanian wolf) and the passenger pigeon, both of which were hunted to extinction within roughly the past century. The de-extinction studies that have perhaps attracted the most attention are those focused on bringing back the woolly mammoth (Mammuthus primigenius). Dating back to approximately 400,000 years ago, these relatives of modern elephants were mostly driven to extinction through a combination of climate change, inbreeding, and hunting about 10,000 years ago, although a few isolated populations survived a few thousand years longer. Frozen mammoth carcasses yielded a complete genome for the animals, and it was fully sequenced in 2015. Genes for the mammoth's hair, fat, and blood proteins have been inserted into laboratory-cultured stem cells from modern-day elephants for study. Mammoth genetic material has also been inserted into an egg cell (ovum) of a living elephant; if viable, this genetic construct could theoretically yield a mammoth–elephant hybrid. Researchers from Russia and South Korea are reportedly seeking the means to clone a mammoth. It should be noted, however, that many technical obstacles—including the crude state of veterinary knowledge and technology for in vitro reproduction for even most living species—still stand in the way of these de-extinction efforts. See also: Elephant; Elephant phylogeny; Phylogeny; Proboscidea; Thylacine: genetics of an extinct species

Technical difficulties aside, de-extinction is a very contentious endeavor in the eyes of many scientists and ethicists. The health and well-being of the individual animals produced by the de-extinction process would be hard to guarantee, which makes the experiments potentially cruel. Similarly, it is hard to know what hazards a pregnant female animal might experience while carrying a fetus from an extinct species. Animal behaviorists have pointed out that the young of many species learn essential behaviors from their parents; thus, for members of these resurrected species, that will never be fully possible. Conservationists have also questioned the goals of de-extinction experiments: If the original natural habitat of an extinct species has disappeared or been transformed, then any species resurrected by de-extinction could survive only in captivity. Proponents of de-extinction, however, have defended it as a possibly essential tool for undoing some of the harm to natural biodiversity that human activities and climate change are causing. See also: Biodiversity; Bioethics; Conservation; Endangered species; Speciation; Species concept

To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.

Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.

About AccessScience

AccessScience provides the most accurate and trustworthy scientific information available.

Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Its dedicated editorial team is led by Sagan Award winner John Rennie. Contributors include more than 9000 highly qualified scientists and 39 Nobel Prize winners.

Features

MORE THAN 8500 articles and Research Reviews covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology

115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms

3000 biographies of notable scientific figures

MORE THAN 17,000 downloadable images and animations illustrating key topics

ENGAGING VIDEOS highlighting the life and work of award-winning scientists

SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research

LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information